Crimped staple fibres



April 5, 1966 JJ R. MURLEY CRIMPED STAPLE FIBRES Filed April 2, 1963GST/EHPs Het-cw- 25A/.577% 'aF 84H5, ss/,Cri

INVENT OR BY @@54/m ATTORNEYS' United States Patent M 3,244,275 CRHMPEDSTAPLE FIBRES John Reginald Murley, Harrogate, England, assigner toImperial Chemical Industries Limited, London, England, a corporation ofGreat Britain Filed Apr. 2, 1963, Ser. No. 259,892 lf2 Claims. (Cl.2015-835) This invention relates to `a `process for making crimpedstaple fibres from synthetic fibre forming polymers, particularly thosemade from polyethylene tereplithalate.

I have found unexpectedly that a 3 dimensional crimp and deformations incross-section can be obtained in staple fibres made from synthetic nbreforming polymers by submitting a bulk quantity of randomly arrangedvfibres to mechanical compression for example :be-tween the platens of a.baling press. Undirectional compression of a bulk quantity ofsubstantially randomly laid fibres has been found to give the desiredresult but it will be appreciated that compression in more than onedirection simultaneously or in succession will give the desired resulte.g, by compressing a bale first in one direction and then at rightangles thereto, under suitable conditions. These conditions are quitecritical but we have determined by research and experiment that they canbe expressed very simply by reference to the ultimate density or truedensity of the fibres which are being so compressed.

I have found that the fibres after suitable compression in thebaie,'have a lesser tendency to recover with the result that retainingstraps which are used for balng such 'fibres do not snap open with agreat force when cut. Moreover and more importantly the fibres aredeformed beyond the elastic limit and also a plastic deformation occursin the cross-section of the fibre. Unexpectedly .these deformations areof such a kind that contrary to expectations the textile processing ofsuch fibres although it requires certain modifications is not onlypossi-ble but in some cases facilitated. Uncrimped fibres of uniformcross-section cannot be processed on normal textile processing machineryincluding carding and spinning but when compressed according to myinvention are found to have sufficient retentivity and cohesion witheach other to allow lap formation and subsequently to make the spinninglof such initially uncrimped fibres into yarns possible.

According to my'invention, therefore I provide a process for makingcrimped staple fibres from synthetic fibre forming polymers,particularly those made from polyethylene terephthalate, comprisingcompressing a bale of substantially randomly arranged fibres to adensity which is at least 50% of the density of a single fibre in thebale and maintaining this pressure for a time sufficient for deformationof the fibres in their longitudinal direction beyond the elastic limitand also of their cross-section involving a plastic deformation to takeplace so that the fibres when released from pressure upon examination4show a 3 dimensional crimp and deforma-tions and at least 20deformations of the cross-section of the bres per linear cm. of thefibre, without any fusing between individual fibres. The deformationsare caused by compressing the fibres in contact with one another until adeforma-tion beyond the elastic limit takes place at their contactingsurfaces. In the case of staple fibres of about 1 to l0 inches in lengthand of deniers between l and l0, the length of the fibre is of coursemany times greater then the diameter and accordingly the deformations ina random array of fibres will be approximately l or 2 fibre diametersalong the length. It will be appreciated that the deforming effect ofone fibre from another with which it is in contact will depend on theangle between 3,244,275 Patented Apr. 5, 1966 ICC the axis of the fibresat the point of contact and upon the inclination of the line Which isperpendicular to the axis of both fibres and which passes through theirmutual point of contact to the direction of external pressureapplication that is to say the line 4of travel of the platens of abaling press.

Generally I have found a compression of a multitude of randomly laidfibres in a bale of 50% to 80% of the density of the single fibre isrequired to yachieve crimping and the deformation of the cross-sectionbeyond the elastic limit. The timing of the compression has an effect onthe recovery of the fibres. The bale should therefore be maintained in ahighly compressed state at a density greater than that of the final balefor a period of at least 1A, preferably about 1/2--1 minute, in order toappreciably reduce the tendency of the bale to recover from itscompressed state. By this meansvit has been found possible to restrain apolyethylene terephthalate fibre ybale of 46 lbs. per cu. ft. densityafter ultimate compression with the same number and size of steel strapsas are necessary on a bale of the same weight but only of ll lbs. percu. ft. density. This lack of recovery has a further advantage inasmuchlas the high density bale when released from its straps expands slowlyand by only a smal.'l amount, compared with the immediate and extensiverecovery of the low density bale which expands to about twice its balelength. I have found that the initial openness or lay of the fibres hasa considerable effect on the pressures which are required to compress abulk quantity to within ythe specified limit, in order to g-et therequired amount of deformation.

If e.g. as occurs in practice, a large tow of crimped filaments is cut,the cut tuftsof fibres tend to cohete due to the presence of finishcomposition on the fibres and due to the mechanical compression duringany previous crimping. Such tufts have a density of about 4 lbs. per cu.ft. in the case of polyethylene terephthalate fibres. If such fibretufts are separated after cutting by a fiuid stream a much looser anddesirably random distribution of bres is obtained.

Compression is commercially conveniently carried out in a baling presscapable of exerting the required compression of the fibres. The fibresmay be crimped by known methods, or uncrimped fibres may be used. In theformer case additional crimp in 3 dimensions is super-imposed on theexisting sinusoidal or saw-tooth crimp; in the latter case a random 3dimensional non-uniformal crimp results provided of course the fibresare substantially randomly distributed during.` compression.Conveniently the fibres are compressed to the required high densityalready in the form of a bale but in this context it will be appreciatedthat by a bale We mean a bulk quantity of fibres exceeding at least 10lbs. in Weight, preferably 10G-200 lbs. in weight.

The invention will be further understoodfrom the following detaileddescription in conjunction with the drawings in which:

FIGURE 1 is a block diagram illustrating the process steps for producingcrimped fibres in accordance with the principles of the presentinvention;

FIGURE 2 is a perspective view of a strapped bale of compressed fibrescrimped by the process of the present invention; and

FIGURE 3 is a graph in which the density of the compressed fibers isplotted against applied pressure.

Iny my British Patent 777,113 an apparatus for baling resilient staplefibers is described using rams having a clearance of at least 1.5 mm.all around in the compression chamber. Bales of fibres can be compressedto a density of about 20 lbs. cu. `ft. i.e. bales with a residualdensity of 11-15 lbs. per cu. ft. can be obtained with such a baler.This is insufficient for the production of fibers of my invention havinga three dimensional crimp and other deformations. However, by modifyingthe design of the baler, we can produce the required high density bales,e.g. by using the ram for feeding the fibers into the chamber, as thehigh compression ram, withdrawing the ram after that compression, untilsufficient fibre has been compressed in a first direction until theprescribed density has been achieved and then continuing the operationas described, by compressing a number of layers using said ram forfeeding the fibers, as part of one side of the compression chamber,before compressing the fibers in a direction at right angles with asecond ram against a quantity of previously compressed fiber and formingthe side of said chamber, thereby also achieving continuous operation.

It will be appreciated that other baling machines may be used which arecapable of compressing fibres to the required density A bale formedaccording to the present invention is illustrated in FIGURE 2. It hasbeen found, unexpectedly, that even these high compression bales whenstrapped are quite safe to handle and that the bale is quite dead, thatis to say, the straps do not snap open when cut, as happens with livebales which endanger the operator when the straps are cut. I have foundythat such live bales are obtained when compressing, for example,polyethylene terephthalate fibres to a density up to 40 lbs. per cu. ft.

Although my description and the examples refer particularly topolyethylene terephthalate fibres, I believe that my invention isapplicable to other synthetic linear polymer fibres such as those madefrom copolyesters based on terephthalic acid, polyamides,polyacrylonitrile, ethylene polymers particularly stereospecicpolypropylene, and other fibre forming vinyl type polymers andpolyoxymethylene.

It should be appreciated that the bulk quantity of super compressedfibres should not be subjected to ya heat setting treatment in thiscompressed form because of the poor heat transfer properties of thefibres and therefore a resultant uneven heat treatment.

As seen in FIGURE 3 when the density, in lb./1cu. ft. of a bulk quantityof fibres is plotted against the applied pressure, in tons per sq. incha curve is obtained which at first rises slowly but then turns steeplyand continues in a substantially straight line with a clearly definablebreak before continuing in the steep rise in a line displacedsubstantially parallel with the line before the break, below. The breakin the line is believed to coincide with the formation of the crimps andthe deformations in the fibres, beyond their elastic limit.

The following examples illustrate but do not limit my invention.

Example 1 A 225,000 denier tow of 11/2 denier polyethylene terephthalatefilaments which have been drawn, crimped and heat set to give 12 to 2Osinusoidal crimps, substantially in one plane, were cut into cotton typestaple lengths of 11/2. The cut staple fibres Were fed into a balingmachine, in principle as described in British Patent 777,113, but in.addition to the slight compression and instead of the light ram, aheavy ram was used, capable of compressing each pre-weighed lot offibres to give a resulting bale density of 64.1 lbs. per cu. ft., whenthe ram formed the top of the compression chamber. At this stage, thesecond ram was brought into operation and the bale was compressed Iatright angles against a previously compressed bale, ejected and strappedas described in British Patent 777,113.

This bale Which had been compressed to a density of 64.1 lbs/cu. ft. wasinert, dead and safe to handle when the straps were cut or openedaccidentally. The fibres had non-uniform three dimensional Icrimp andthey could be peeled off in leather-like layers and on working by handquickly assumed a desirable bulk and soft handle. Satisfactory laps offibres weighing 131/2 ozs. per sq. yard were prepared.

Although it is not stated in the example, I have found that thedistribution of finish which had been applied to the filaments isimproved in my bales.

Example 2 A bale containing 11/2 denier crimped and heat-setpolyethylene terephthalate fibers 11/2 long and prepared on a balingmachine as described in principle in British Patent 777,113 ofdimensions 20 x 18 X 42" with 4 straps passing across the 20 edge andencompassing the bale longitudinally is placed in a vertical hydraulicbaling press. The direction of travel of the platens is vertical and isparallel to the longest dimensions of the bale. The bale density is 11lb./ cu. ft. In the top and bottom platens of the press there are grovesto accommodate the straps. The straps are tightened when the platens,originally a distance of 42 apart at the beginning of the compressionstroke, are closed to 8". The force required to effect this compressionis 320 tons. Those four sides of the bale which are not in contact withthe platens are not supported in any way. The bale is then compressedfurther by a force of 560 tons. This pressure is maintained for 30seconds. The separation of the platens is now 7 the density about 66lbs. per cu. ft. When the pressure is released the bale bulges betweenthe straps. The approximate height of the bale is 14 inches.Surprisingly' the bale expands in height but there is little change inthe other dimensions. The bale density is 45 lbs/cu. ft. This bale isinert, dead and safe to handle when the straps are cut or openedaccidentally. The fibres have a nonuniform, three dimensional crimp and60 deformations of cross-sections per inch. Only the usual amount ofdisturbance of the bres as used with bales of a density of 11-20 lbs.per cu. ft. is required when transferring the fibres to the aprons of anopening line, to restore the usual bulk. Satisfactory laps of fibresweighing 13`1/z oz. per sq. yard have been prepared.

Example 3 Three slabs of high density bales prepared as described inExample 2 are pressed lightly together and strapped, the straps areremoved before combining the three slabs. With each of the slabsweighing lbs., a bale weighing 360 lbs. is obtained occupying a volumeof only 3A of a 120 lb. -bale having a density of only l1 lbs. per cu.ft. This illustrates the saving which can be obtained in warehouse spaceand in shipping costs with my bales.

Example 4 A 120 lb. bale of randomly laid polyethylene terephthalatestaple fibers 11/2" long and of 11/2 denier the fibres having anultimate density of 86 lbs. per cu. ft. is compressed in a superdensityhydraulic baling press. The initial bale has an overall height of 40inches and 36 inches across the straps and having .a bulk density of17.9% of the ultimate density. This bale is further compressed t0 anoverall height of l5" and measuring 11" across the straps when releasedfrom pressure and having -a bulk density of 52% of the ultimate densityin its strapped condition. The bale is placed axially between theplatens of the high density hydraulic press which are slotted toaccommodate the straps, the load is raised to 40,000 tons bale weight(lbs.)

the length of the bale in inches is then equal to bale weight (lbs.)

The density is 68% of the ultimate density. The bale is then strappedwith four straps to give a strap tension of 50 l-bs. per sq. inch on apower tool and the straps are sealed. The load on the platens of thepress is then increased to 600 tons and held at this pressure for 1minute until yielding of the libres is complete. The density is 77% ofthe ultimate density of the libres in this condition. The load is thenreleased and the bale expands to an effective length in inches of baleweight divided .by 10.5. This resutls in the density of the bale of 52%of the ultimate density.

Example 5 Three high density bales .are combined in the same press andusing the procedure as in the previous example, but the original strapsare retained and the combination of -bales is secured by a separate setof four straps.

Example 6 A bale of polypropylene is prepared using an apparatus asdescribed in British Patent 777,113, a load of 350 tons is used tocompress a bale so obtained, the bulk density of the polypropylenelibres was 38 lbs. per cu. ft., compared with 58 lbs. per cu. ft. forthe polyethylene terephthalate libres. Both these densities areequivalent to about 67% of the ultimate density of the libre. Theindividual libres when examined under the microscope were found to besimilarly deformed as the polyethylene terephthalate libres.

Example 7 A bale of polyethylene terephthalate staple libres 11/2 denier11/2 which had not been crimped but which were coated with a spin linishsolution of polyethylene glycol monolaurate and a corrosion inhibitorwere compressed into a high density bale as described in Example 4. Onexamination the libres showed permanent deformations on the long andshort libre axes. The libres were subjected to normal processingconditions at a temperature of 76 F. Iand 38% relative humidityresulting in a satisfactory 1A() S cotton count yarn.

Two weights of opener lap were made, lirstly, one of 13 oz. per yard andsecondly one of 17 oz. per yard. The lighter lap licked at unrolling butthe heavier lap did not. There was 4a deposit of loose libres thrown outat the drawing stages. This example illustrates that the libres can beprocessed on the cotton system without previous crimping.

What I claim is:

1. A process for imparting three-dimensional crimp to a mass of shortlengths of libres of synthetic libre forming polymer comprising:compressing as a unit the whole mass of said fibres which are randomlyarranged in contact with each other to a density which is at least asgreat as 50% of the density of a single libre; and maintaining thiscompressive pressure for a period of time to cause deformation of amajority of the libres in their longitudinal direction beyond theirelastic limit and to cause plastic deformation in the cross section of amajority of the libres thereby producing a three-dimensional crimp and.at least 20 deformations of each libre per linear centimeter thereofwithout any fusing between individual libres.

2. A process according to claim 1 in which the deformations are causedby compressing the fibres in contact with one another until adeformation beyond the elastic limit takes place on their contactingsurfaces and in which the libres are l to inches in length and of adenier between 1 and 10. l

3. A process according to claim 1 in which a multitude of randomly laidlibres in said mass are compressed 50% to 80% of the density of a singlelibre.

4. A process according to claim 1 in which said mass is maintained in ahighly compressed state at a density greater than that of the final massfor a period of at least 1A minute.

S. A process according to claim 1 in which the libres are separated andopened after cutting by a liuid stream to obtain a looser desirablyrandom distribution of libres 4before compressing in .a bale.

6. A process according claim 1 in which the quantity of libres -beingcompressed exceeds 10 lbs. in weight.

7. A process according to claim 1 in which the libres are syntheticlinear polymer libres of a libre forming polymer selected from the groupconsisting of polyethylene terephthalate, copolyesters based onterephthalic acid, polyamides, polyacrylonitrile ethylene polymersparticularly stereo-specilic polypropylene and libre formed vinyl typepolymers and polyoxymethylene polymer.

8. A process of imparting three-dimensionl crimp to short lengths oflibres of synthetic libre-forming polymer comprising: mechanicallycompressing into the form of a self-supporting bale at least a ten poundmass of said libres which are randomly arranged in contact with eachother, said compressing step being effected by a pressure such that,when compression pressure is plotted against the density of the mass oflibres there is obtained a curve which at lirst rises slowly but thenturns steeply and continues in a substantially straight line with aclearly definable break before continuing in the steep rise in a linedisplaced substantially parallel with the line before the break; andmaintaining this compressive pressure for a period of time to causedeformation of a lmajority of the libres in their longitudinal directionbeyond their elastic limit and to cause plastic deformation in the crosssection of a majority of the fibres thereby producing a threedimensionalcrimp and at least 20 deformations of each libre per linear centimeterthereof without any fusing between individual libres.

9. A strapped compressed bale of randomly arranged unfused staple libresof polyethylene terephthalate, said libres being of substantiallyuniform density and having a three-dimensional crimp and .at least 20deformations of each libre per linear centimeter thereof, said balehaving a mass of at least ten pounds and a density which is at least asgreat as 50% of the density of a single fibre, said bale having areduced tendency to expand after having been compressed and therebyhaving a reduced tendency to cause baling straps to snap open when thestraps are cut.

10. A compressed -bale as in claim 9 wherein said libres are between 1and 10 inches in length and of deniers between 1 and l0, saiddeformations in the random array of fibres being about l to 2 librediameters along the lengths of said libres and occ-urring at thecontacting surfaces of said libres.

11. A compressed bale as in claim 9 wherein said polyethyleneterephthalate libres are about one and one-half inches in length.

12. A compressed bale as in cla-im 11 wherein said polyethyleneterephthalate libres have la spin linish uniformly distributed thereon.

References Cited by the Examiner UNITED sTATEs PATENTS 2,311,174 2/1943Hitt i 19-66 2,539,725 1/1951 carahei 2o6 83.5 2,647,285 8/1953 Piau28-72 2,707,806 5/1955 Wilkie. 2,780,838 2/1957 Wilkie 20s- 83.5 X

FOREIGN PATENTS 338,269 6/1921 Germany.

THERON E. CONDON, Primary Examiner. DONALD w. PARKER, Examiner.

L. K. RIMRODT, I. M. CASKIE,

Assistant Examiners.

9. A STRAPPED COMPRESSED BALE OF RANDOMLY ARRANGED UNFUSED STAPLE FIBRESOF POLYETHYLENE TEREPHTHALATE, SAID FIBRES BEING OF SUBSTANTIALLYUNIFORM DENSITY AND HAVING A THREE-DIMENSIONAL CRIMP AND AT LEAST 20DEFORMATIONS OF EACH FIBRE PER LINEAR CENTIMETER THEREOF, SAID BALEHAVING A MASS OF AT LEAST TEN POUNDS AND A DENSITY WHICH IS AT LEAST ASGREAT AS 50% OF THE DENSITY OF A SINGLE FIBRE, SAID BALE HAVING AREDUCED TENDENCY TO EXPAND AFTER HAVING BEEN COMPRESSED AND THEREBYHAVING A REDUCED TENDENCY TO CAUSE BALING STRAPS TO SNAP OPEN WHEN THESTRAPS ARE CUT.